Phonograph needle



Dec. 16, 1930. o mso r 1,784,845

PHONOGRAPH NEEDLE Filed Oct. 4, 1928 //v VENTOH Laws .4. MORRISON Patented Dec. 16, 1930 UNITED STATES PATENT OFFICE LOUIS A. monarson, or BROOKLYN, NEW YORK, ASSIGNOR TO BELL TELEPHONE minoaa'romns, .INGQBEQBAQ PB F I EW YORK, N. Y., A CORPORATION or NEW YORK PHONOGRAPH NEEDLE Application filed October 4, 1228. Serial No. 310,259.

This invention relates to reproducers adapted to be used for playing-back original soft wax records and more particularly to a needle suitable foi such i eproducers.

It is the object of-this invention to provide a needle of this sort which is of sturdy construction, easy to make, and of the permanent type.

In addition to these features it is understood of course that a playback needle must be very light and very stiff to reproduce records faithfully and without injury to the soft wax. All of these requirements are met satisfactorily by a needle having a body portion of light weight wood fitted with a sapphire point and covered with a thin coating of duralumin paint. As the point is very durable the needle preferably is secured permanently to the diaphragm.

In the drawing, Fig. 1 shows the needle of this invention applied to one type of re.- producer, and

Fig. 2 is a detail view of the needle.

These needles are particularly adapted for use with reproducers of either the electromagnetic or the electrodynamic type in "which theyfiex.the diaphragm about one of its diameters. Fig. 1 discloses one form of electrodynamic or moving coil reproducer with which these needles may be advantageously used. 'The diaphragmlis adapted to flex about the diameter normal to the plane of the drawing and is stiffened against flexure at right angles to this axis by groove 2. Groove 3 further stifiens the diaphragm against local fiexurc of the portion in contact with the needle 4. A suitable coil 5 carried by the diaphragm moves with it in an annular gap between pole pieces 7-7' and another magnetic member 8. An exciting winding 9 produces a steady flux in the gap so that movements of the needle are transundesirable local vibration in the needle and in the diaphragm is prevented by making the needle base unusually large thereby giving the needle very great inherent stiffness and providing large area of contact ,with the diaphragm.

The construction of the needle 4 is clearly shown in Fig. 2 in which the main body portion 10 is shown as a cone of balsa wood with a non-linear taper. Grooves 11 and 12 in the base of the cone correspond to grooves 2 and 3 in the diaphragm and insure that the needle will be properly located on the diaphragm when it is secured in place. The sapphire point 13 is permanently cemented into the end of the cone and the coating of metal paint 14 is sprayed on the body portion to a thickness of about 10 mils (for a needle 1 inch long).

Obviously the body portion need not be exactly as shown but may take any form which results in a needle of the proper weight and stiffness. It also will be understood that for best results the thickness of the metal coating should be varied in accordance with the diameter and length of needle employed. The low mass and high stiffness ralumin and fitted with a sapphire point, the

base diameter of the body being comparable to its length.

4:. In an electrical pick-up device a moving system including a wooden needle of large base diameter coated with metal and attached to a diaphragm.

4. In an electrical pick-up device a moving system including a wooden needle of large base diameter attached to a diaphragm the needle being coated with metal and fitted with a permanent point.

5. In an electrical pick-up device a moving system including a balsa wobd needle, of large base diameter attached to a dia phragm the needle bein alumin paint and fitte point.

coated with durwith a sapphire In witness whereof, I hereunto subscribe my name this 29th'da of Se tember, 1928.

LOUI

ORRISON. 

